Detonator



Sept. 23,- 1958 l. o'rKlN ErAL 2,853,012

` DETONATOR VFiled oet. 1s, 195e INVENTOR. ISRAEL ROTK/N ./7 7 TOR/VE YJ.

BSEL/M SEYMOUR POU/VOS Uite States ate DETONATOR Israel Rotkin, Silver Spring, Md., and Selim Seymour Porlnos, Washington, D. C., assignors to the United States ofAmerica as represented by the Secretary of the Army Application October 18, 1956, Serial No. 616,898

2 Claims. (Cl. IGZ-70.2)

(Grantedunder Title 35, U. S. Code (1952), sec. 266.)

The invention described herein may be manufactured and used by or for the Government for governmental purposes without payment to us of any royalty thereon.

i This invention relates to detonators and more particularly to detonators responsive to either a mechanical impulse or an electrical signal.

Ordnance explosive devices areV often red by an electrical pulse passing through a detonator. Also these same devices often have a mechanical impact detonator or primer. The electrical pulse is typically produced by an electronic proximity detecting element, a piezoelectric impact. element, or a battery-switch combination. The mechanical impact is typically produced by target impact, a graze sensitive device, or a clock timing device. In presently used fuzes of this design, two detonators are used, one for each type of initiation. This is notI entirely satisfactory because itis not possible to align both detonators in an optimum position with reference to the next element of the explosive train, usually a tetryl lead.

At present they principal methods of providing safety for mechanical impact detonators are by either restraining the firing pin or offsetting some element in the tiring train or a combination of these. This is a severe design limitation and it would be desirable to have a mechanical type detonator with electrical safety features.

An object of this invention is to provide a combination detonator sensitive to either electrical energy or mechanical impact.

Another object is to provide a detonator sensitive to mechanical impact which is armed electrically by operation of a switch.

Further objects are to achieve the above with a device that is sturdy, simple, and reliable, yet cheap and easy to manufacture.

The specific nature of the invention as well as other objects, uses, and advantages thereof will clearly appear from the following description and from the accompanying drawing, in which:

Fig. l is a sectional view of a detonator in accordance with this invention.

Fig. 2 is a sectional View of a modied form of the invention with associated electrical circuits shown schematically.

Fig. 3 is a sectional view of another modied form of the invention with associated electrical circuits shown schematically.

As seen in the drawing, the basic concept of this invention is to package a piezoelectric element 10 in a ycase 12 which also contains the conductive bridge 14, ilash powder 16, and explosive charge 20. Provisions are made in the embodiments shown in Figs. 2 and 3 to provide for an electrical safety and arming system 'and for remote lelectrical tiring.

Specifically the embodiment shown in Fig. 1 has a cylindrical metal case 12 which contains at the lower end an explosive charge 20. Immediately above the base charge is priming charge 22 which, when initiated by i i. t i l .2,853,012 Patented Sept. 23, 1958 iiash charge16, in turn initiates the explosive charge.A 20. The piezoelectric element 10 is in the form of a washer, coaxial with the case 12, and adjacent the upper end` of the case. The washer 10 and all the other elements in the detonator are held tightly in place by crimping the top edge of the `case 'at 24. Contacting the upper face of piezoelectric washer 1t) is a conductive element 26 which is in the form of a disc coaxial with the washer 10. Coaxial rod 28 depends from element 26. Conductive washer 30 contacts the lower facer of piezoelectric washer 10 land is also coaxial with it. Rod 28 extends throughthe central aperature of both washers 10` and 30 and. fis insulated from washert) by an annular band of insulating material 32. Band 32 extendsthe full length of rod 28 because it is easier to m'anufacturein this manner. The bottom of rod 28 is ilush with the bottom of washer 30. Coaxial'with washeri30 is a thin conductor 14, in this case a carbon disc, which contacts both the lower surface'` of this washer and the end of rod 23.

When the piezoelectric element 10 is stressed it develops an electrical `potential between its upper and lower faces. Thiselectrical potential is transmitted to the lower surface ofA rod 28` and washer 30 and causes a current ilow through a narrow annular portion of disc 14 adjacent annular insulating band `32. This. annular portion of disc 14 is the` only functional portion; however, it has been found easier to apply a` disc than any other shape of resistance material.l Of course, other resistance elements known to the art, such as spark gap, wire bridge, or conductive mixes, could be used instead of carbon disc. 14.T

The current owing through the narrow annular portion of disc 14 causes it to become hot and ignite the dash charge 16. The igniting of ilash charge 16 initiates the priming charge 22 which in turn initiates the explosive charge 20.

The method of stressing the piezoelectric element 10 may be chosen from any of the presently known methods of ring mechanical impact detonators, such as acceleration sensitive weights or spring biased plungers released by clock mechanisms. Element lll may be any of several piezoelectric materials-barium titanate, for example.

The embodiment of the detonator assembly illustrated in Fig. 2 is similar to the embodiment of Fig. 1, except as noted below. The case 12 has a second crimp 34 which forms electrical contact between the case and conductive washer 30. The top crimp 24 does not make electrical contact with conductive element 26 in this embodiment. A first external electrical lead 36 is connected to the case 12 and a second external electrical lead 38 is connected to conductive element 26. When switch 40 is in the safe position, the conductive element 26 is connected to conductive washer 30 through a low resistance path. This shunts the high resistance path through the `carbon disc 14 so that the detonator is in an inoperative condition. When switch 40 is in an armed position, it connects source of electrical energy 42` between conductive element 26 and washer 30. This permits operation of the fuze 'by two methods, the lirst of which is by stressing the piezoelectric element 10 in the manner described above. The second method is by applying an electrical pulse from source 42. Because the piezoelectric element 10 is an insulator, the electrical ow will be through lead 36, case 12, washer 30, disc 14, element 26, lead 38 and switch 40.

The source of electrical energy 42 has been represented on the drawing as a battery and switch in series. It will be understood that this source could be of various forms well known to the art, such as an electronic proximity circuit or a remotely located piezoelectric element.

The embodiment of the detonator assembly shown in Fig. 3 is similar to the embodiment of Fig. 2 except as noted below. In this embodiment a conductive element 27 in the form of -a washer contacts the upper face of piezoelectric element 10. The insulating material 32 extends betzween rod 28 and element 27. First lead 36 connectsatheV case '12 to source-off'electrical energy 42. Second leadv 38Aconnects 'the sourceI 42 to washer-shaped conductiveelement27. v -Arming switch 44 connects element 27 with rod 28. When switch 44 is open, the upper face "of element is disconnected from rod 28 and there is` -no'path for current to ow through the rod, hence the detonator is safe. When switch 44 is closed or armed, there-is a pathWfor current flow from the upper face of element'10 through lead 38, switch 44, rod 28, disc 14, and `washer 30 to the lower face of element 10. This permits a mechanical stress or impact on lthe piezoelectric element to vfire the detonator. Also with switch 44 closed there isfa-path for currentfflow from source 42 through switch 44, rodl 28, disc 14, washer 30, case 12 and lead 36-toback to source 42. This permits electrical energy from a remote source to also re the detonator.

vvSilver paint, or-a similar conductive coating, may conveniently be used to provide equivalents of conductive element 26, rod 28, and conductive washer 30. The upper, lower, and inner4 surfaces of element 10 may be coated with such paint. The necessary electrical insulation between element 30 and the lower end of element 28 may then be provided by-cutting a circular groove through the layer of paint on the underside of element 10. Such circular groove should be only slightly larger in diameter than the central hole of element 10.

It will be apparent that the embodiments shown are only exemplary and that various modifications can be made in construction, materials, and arrangement within the scope of the invention as defined in the appended l'aimsr. l

4 We claim: v 1. A detonator assembly comprising: 'a cylindrical case,r

an explosive charge contained within the case, a washer of piezoelectric material adjacent one end of the case and 4 coaxial therewith, a washer of conducting material con# tacting one side of the piezoelectric washer and coaxial j therewith, a thin disc of carbon contacting the other side of the conducting washer and coaxial therewith, ash powder contacting both the carbon disc and the explosive charge, and a conductive element contacting the other side of the piezoelectric washer, said conductive element having a rod extending through the central apertures of the two washers insulated from the conducting washer and contacting the thin carbon disc whereby impact applied to the piezoelectric washer will produce an elec-1 trical potential between the conductive washer and the conductive element, which potential will cause a current to flow through a portion .of the thin carbon disc which will in turn ignite the flash powder and explosive charge` 2. The invention #as defined in claim l, there being p' additionally provided: a source of electrical energy, a first 'l switch in series with said source, and a second switch having a safe position and an armed position, said second switch Ibeing connected so that it electrically shorts Y said carbon disc when in the safer position, and connects said carbon disc in series with said source when in the armed position.

References Cited in the le of this patent f UNITED STATES PATENTS 

